Editing CMS Pipelines (section)

==Features==
The concept of a simple pipeline is extended in these ways:
* A program can define a subroutine pipeline to perform a function on all or part of its input data.
* A network of intersecting pipelines can be defined. Programs can be in several pipelines concurrently, which gives the program access to multiple data streams.
* Data passed from one stage to the next is structured as records. This allows stages to operate on a single record without the no need for arbitrary buffering of data to scan for special characters that separate the individual lines.
* Stages normally access the input record in locate mode, and produce the output records before consuming the input record. This lock-step approach not only avoids copying the data from one buffer to the next; it also makes it possible to predict the flow of records in multi-stream pipelines.
* A program can dynamically redefine the pipeline topology. It can replace itself with another pipeline, it can insert a pipeline segment before or after itself, or both. A program can use data in the pipeline to build pipeline specifications.

''CMS Pipelines'' offers several features to improve the robustness of programs:
* A [[syntax error]] in the overall pipeline structure or in any one program causes the entire pipeline to be suppressed.
* Startup of the programs in the pipeline and allocation of resources is coordinated by the ''CMS Pipelines'' dispatcher. Individual programs can participate in that coordination to ensure irreversible actions are postponed to a point where all programs in the pipelines have had a chance to verify the arguments and are ready to process data. When the pipeline is terminated, the dispatcher ensures resources are released again.
* Errors  that occur while  data  flow  in  the  pipeline  can  be  detected  by  all  participating  programs. For example, a disk file might not be replaced in such circumstances.